This invention relates to an image processing device which is capable of converting a captured image to an image desired by the user, for example, converting a photo to an image like an illustration for use in devices such as a personal computer, a word processor, a work station, an office computer, a portable information tool, a copying machine, a scanning device, a facsimile, a television, a video cassette recorder, and a video camera, and further relates to an image processing method.
Conventionally, in the case when an image like an illustration is generated from a photo or an image, the most common method is that a skillful worker draws the image by hand. This process demands an extremely special technique and a high skill; therefore, this work cannot be done by every worker. Further, since this work is conducted by hand, this work is a time-consuming process and is not suitable for mass production.
Therefore, recently, in order to realize a shorter working hours and mass production, the use of an image processing device mounted on devices such as a personal computer and a word processor has been studied so as to generate an image like an illustration. For example, a line image is extracted(line extracting operation) and colors are subtracted(subtractive process).
As the method for extracting a line image, for example, a method which adopts a Sobel filter has been used. This method makes it possible to extract an edge portion in an image by using a simple algorithm; however, this method has drawbacks such as a line varying thickness for each portion. Further, the subtractive process, which has been commonly used, is performed in accordance with a histogram of a pixel value(RGB value or brightness value); thus, another drawback appears as follows: a part to be integrated into one color, for example, a part smoothly varying brightness(gradation) is divided into a plurality of colors in an image.
Moreover, as a method for converting an image such as a photo into an image like an illustration, for example, inventions such as an xe2x80x9cimage processing methodxe2x80x9d (Japanese Published Examined Patent Application No.2685458 (Applicant; Canon Inc. Tokukaihei 1-109479, published on Apr. 26, 1989)) have been devised. In the above-mentioned image processing method, an edge is extracted and an area surrounded by the edge is filled with a certain color so as to generate an image like an illustration.
However, in the xe2x80x9cimage processing methodxe2x80x9d of the patent application number 2685458, an edge is extracted and an area surrounded by the edge is filled with a certain color; thus, the edge needs to constitute a closed area without any disconnection so that upon extracting an edge for a full-color image, in some images, a large number of small areas appear, or a closed area is not extracted at all. Thus, in some images, it is difficult to generate a desired illustration image.
Further, in the above-mentioned image processing method, an edge portion is not converted so that an original image partially remains on a generated illustration image, resulting in an unnatural image in some cases.
The object of the present invention is to provide an image processing device and an image processing method which are capable of generating a natural illustration image from any kind of original image in response to the need.
In order to achieve the above-mentioned objective, the image processing device of the present invention, which performs an image processing operation on the inputted original image, is provided with an image compositing section which allows the original image to undergo a subtractive process so as to generate a subtractive image, generates a line image from the original image, and produces a composite image of the subtractive image and the line image.
In the above-mentioned arrangement, the original image is, for example, an image such as a digitized color photo. Further, the subtractive process is, for example, a process in which the original image is divided into a plurality of areas, and each of the areas is painted by using one color so as to visually enlarge a size of a pixel constituting the image, thereby simplifying the image. Furthermore, the line image is, for example, a binary image which is constituted by a black line and a white area so as to generate an edge surrounding an object of the original image.
Moreover, in the above-mentioned arrangement, the image compositing section allows the original image to undergo the subtractive process so as to generate a subtractive image, generates the line image from the original image, and produces a composite image of the subtractive image and the line image.
With this arrangement, unlike an image processing device which generates a line image constituted by an edge image and colors an area surrounded by the edge(closed area); a line image does not need to be a closed area. Hence, it is possible to prevent extraction of a number of small closed areas. Further, it is also possible to prevent a state in which no closed area can be extracted. Therefore, a natural composite image can be produced in accordance with the actual image.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.